The present invention generally relates to an energy storage system and, more particularly, to an energy storage control module to be incorporated into a hybrid electric motor vehicle to control the storage and usage of high voltage energy.
Over the past few years, there has been a growing concern over global climate change due to an increase in carbon dioxide levels as well as oil supply shortages. As a result, automobile manufactures and consumers are beginning to have a greater interest in motor vehicles having low emissions and greater fuel efficiency. One viable option is a hybrid electric vehicle (HEV) which allows the vehicle to be driven by an electric motor, combustion engine, or a combination of the two.
Though various features are important to the overall HEV design, the system which stores the energy available for use by the vehicle is a key component. The energy storage system is provided within the HEV to store the energy created by a generator in order for that energy to be available for use by the hybrid system at some later time. For example, the stored energy may be used to drive an electric motor to independently propel the motor vehicle or assist the combustion engine, thereby reducing gasoline consumption.
However, energy storage systems face a variety of design complications, such as over-heating, weight, complexity, ease of incorporation into the vehicle, ease of service, service life and cost, just to name a few. Additionally, known energy storage systems utilize a specific and known number of battery packs and are designed to meet a particular HEV design specification, including a defined service life.
Numerous hybrid systems have been proposed which are statically designed to protect the service life of the battery packs. Typically, those hybrid systems include battery usage constraints which are programmed into the hybrid control module at the time of production to keep the battery in a good usage state for a certain service life, such as a warranty or contract obligation. If the operating temperature of the battery is too high, or short term amperage is too much, the hybrid control module will restrict or limit usage of the battery. However, these systems sacrifice potential fuel-economy for the vehicle each time they prevent the battery from being utilized. This often happens much more than necessary, as the manufacturer often conservatively assumes the worst with respect to the operation of the HEV in order to ensure that all vehicles meet their defined service life goal. Over the course of time, these restrictions upon the usage of the battery can amount to a significant reduction in the efficiency of the HEV. While this often leads to a battery life that significantly exceeds its defined service life, it would preferred to have that extended life exchanged for more usage and ultimately, increased fuel efficiency, given that the battery can often be replaced for a lesser cost.
In order to determine the battery usage limits, typically a number of laboratory tests are run based upon a predicted usage of the battery in customer applications. These predictions are often not very accurate as they are often quite conservative in order to prevent failure under the more extreme operational circumstances. However, this leads to a significant sacrifice with respect to an optimal balance between battery-life and fuel efficiency of the vehicle.
Thus, there is a need for improvement in this field.